When chewing gum is placed in storage for a period of time, it is gradually exposed to the atmosphere as oxygen and other atmospheric components migrate through the packaging material and into the chewing gum. Over time, this exposure to the atmosphere causes chewing gum flavor components to oxidize and develop undesirable sensory characteristics. The oxidation of mint oils in chewing gum is of particular concern. Also, the oxidation of stick chewing gum components is a particular problem due to the high amount of exposed surface area.
Techniques have been developed for including an antioxidant in the packaging material in order to alleviate the oxidation of the chewing gum contained therein. U.S. Pat. No. 5,064,698, issued to Courtright, et al., and the corresponding PCT Publication WO 90/09273, disclose a chewing gum wrapping material prepared by laminating a foil layer and a tissue layer with a wax layer that contains 40% microcrystalline wax, 40% paraffin wax, and 20% polymeric beads, wherein the polymeric beads have been impregnated with an oxygen scavenger made from iron oxide and activated charcoal. The reference teaches that, alternatively, the polymeric beads may be impregnated with (1,1-dimethylethyl)-4-methoxy phenol (BHA) or 2,6-di-tert-butyl-para-cresol (BHT). The polymeric beads contain micropassages formed during polymerization, which facilitate their impregnation with the oxygen scavenger. The wax, which is oxygen-permeable, serves the function of immobilizing and adhering the beads on an inside surface of the tissue layer.
U.S. Pat. No. 4,880,696, issued to Yanidis, discloses the use of BHT in a flexible packaging material. The BHT is incorporated into a polymer composition that is extrusion coated onto a substrate, such as paper coated with polyvinylidene chloride. A heat seal polymer layer is placed over the antioxidant-containing layer, which prevents evaporation of the antioxidant. Eventually, the antioxidant migrates through the heat seal polymer layer to help preserve food packaged in the material.
U.S. Pat. No. 4,248,576, issued to Birks, et al., discloses coating compositions containing paraffin wax mixed with various polymer materials, for coating onto thermoplastic films of polyethylene, polypropylene or polyethylene terephthalate. The coating compositions can also contain a small amount of BHT. The coated structures can be used for packaging.
While it is known to incorporate antioxidant in a packaging material to help stabilize the contents of the package, the packaging materials and methods heretofore used have been relatively complex and expensive. There is a need or desire in the chewing gum industry for an antioxidant-containing packaging material which prolongs the shelf life of chewing gum without adding significantly to the complexity or cost of conventional packaging materials. This need is particularly apparent in the case of chewing gum sticks which, due to their high surface to volume ratios, require a relatively high quantity of packaging material.